Oscillator with tapped inductor

Abstract

The present invention provides an oscillator including a tapped inductor and a cross-coupled pair. The tapped inductor includes a first terminal, a second terminal, a first tap and a second tap. The cross-coupled pair receives two input signals from the first terminal and the second terminal to generate two output signals to the first tap and the second tap, respectively.

What is claimed is: 
     
       1. An oscillator, comprising:
 a tapped inductor comprising a first terminal, a second terminal, a first tap and a second tap; 
 a cross-coupled pair, wherein the cross-coupled pair receives two input signals from the first terminal and the second terminal to generate two output signals to the first tap and the second tap, respectively; and 
 a capacitor coupled between the first tap and the second tap, wherein a first node of the capacitor is directly connected to the first tap, and a second node of the capacitor is directly connected to the second tap. 
 
     
     
       2. The oscillator of  claim 1 , wherein the two input signals comprise a first input signal and a second input signal, the two output signals comprise a first output signal and a second output signal, and the cross-coupled pair comprises a first device and a second device; and the first device receives the first input signal from the second terminal to generate the first output signal to the first tap, and the second device receives the second input signal from the first terminal to generate the second output signal to the second tap. 
     
     
       3. The oscillator of  claim 2 , wherein the first device is implemented by a first transistor, a gate electrode of the first transistor is coupled to the second terminal, and a drain electrode of the first transistor is coupled to the first tap; and the second device is implemented by a second transistor, a gate electrode of the second transistor is coupled to the first terminal, and a drain electrode of the second transistor is coupled to the second tap. 
     
     
       4. The oscillator of  claim 1 , wherein the tapped inductor is a multi-turn tapped inductor. 
     
     
       5. The oscillator of  claim 1 , wherein the tapped inductor comprises a first inductor, a second inductor and a third inductor connected in series, the first inductor is coupled between the first terminal and the first tap, the second inductor is coupled between the first tap and the second tap, and the third inductor is coupled between the second tap and the second terminal. 
     
     
       6. The oscillator of  claim 5 , wherein the two input signals comprise a first input signal and a second input signal, the two output signals comprise a first output signal and a second output signal, and the cross-coupled pair comprises a first device and a second device; and the first device receives the first input signal from the second terminal to generate the first output signal to the first tap, and the second device receives the second input signal from the first terminal to generate the second output signal to the second tap. 
     
     
       7. The oscillator of  claim 6 , wherein the first device is implemented by a first transistor, a gate electrode of the first transistor is coupled to the second terminal, and a drain electrode of the first transistor is coupled to the first tap; and the second device is implemented by a second transistor, a gate electrode of the second transistor is coupled to the first terminal, and a drain electrode of the second transistor is coupled to the second tap. 
     
     
       8. The oscillator of  claim 5 , wherein the first inductor, the second inductor and the third inductor have the same polarity. 
     
     
       9. The oscillator of  claim 5 , wherein the first terminal is a positive terminal for the first inductor, the first tap is a positive terminal for the second inductor, and the second tap is a positive terminal for the third inductor; or the first terminal is a negative terminal for the first inductor, the first tap is a negative terminal for the second inductor, and the second tap is a negative terminal for the third inductor. 
     
     
       10. An oscillator, comprising:
 a tapped inductor comprising a first terminal, a second terminal, a first tap and a second tap; and 
 a cross-coupled pair, wherein the cross-coupled pair receives two input signals from the first terminal and the second terminal to generate two output signals to the first tap and the second tap, respectively; and 
 wherein the tapped inductor comprises a first inductor, a second inductor and a third inductor connected in series, the first inductor is coupled between the first terminal and the first tap, the second inductor is coupled between the first tap and the second tap, and the third inductor is coupled between the second tap and the second terminal; 
 wherein the first terminal is a positive terminal for the first inductor, the first tap is a positive terminal for the second inductor, and the second tap is a positive terminal for the third inductor; or the first terminal is a negative terminal for the first inductor, the first tap is a negative terminal for the second inductor, and the second tap is a negative terminal for the third inductor. 
 
     
     
       11. The oscillator of  claim 10 , wherein the two input signals comprise a first input signal and a second input signal, the two output signals comprise a first output signal and a second output signal, and the cross-coupled pair comprises a first device and a second device; and the first device receives the first input signal from the second terminal to generate the first output signal to the first tap, and the second device receives the second input signal from the first terminal to generate the second output signal to the second tap. 
     
     
       12. The oscillator of  claim 11 , wherein the first device is implemented by a first transistor, a gate electrode of the first transistor is coupled to the second terminal, and a drain electrode of the first transistor is coupled to the first tap; and the second device is implemented by a second transistor, a gate electrode of the second transistor is coupled to the first terminal, and a drain electrode of the second transistor is coupled to the second tap. 
     
     
       13. The oscillator of  claim 10 , wherein the tapped inductor is a multi-turn tapped inductor.